Without speed trim the flare would become very difficult bcs the stick force / g would change in a way that makes the required control input a function of too many parameters f(thrust change, rate of decent, runway slope, inertia, wind changes etc)
If that were the case you would expect at least a note with a warning in the relevant QRH checklist, but instead it just says: Continue normal operation. Had it happen once and it was actually nicer to fly without the speed trim than with.